Zenith racetrack, what is the bracket for?

[tom2]

Gee I hope I have not posted this before, I looked and cannot find it. Anyway. On a Zenith racetrack oval bakelite, there is a rectangular slot at the top back. There is a rectangular piece held on there with two screws. Some sort of bracket or cover device, but for what? I thought it might be to allow some sort of adapter for wall mounting, or some accessory. It has no visible purpose, and I cannot believe they would go to the expense of adding the parts for no reason. Extra production costs, but pennies times many thousands. :